AbstractIn a new book and accompanying research, I demonstrate that markets as neither perfectly efficient nor completely inefficient. Rather, they are inefficient enough that money managers can be compensated for their costs through the profits of their trading strategies and efficient enough that the profits after costs do not encourage additional active investing. Understanding how to trade in this efficiently inefficient market provides a new way to analyze investment strategies, including equity strategies, macro strategies, and arbitrage strategies. These ideas are illuminated further by interviews with leading hedge fund managers Lee Ainslie, Cliff Asness, Jim Chanos, Ken Griffin, David Harding, John Paulson, Myron Scholes, and George Soros.